<template>
  <div>
    <p>请选择你要购买的书籍</p>
    <ul>
      <li v-for="(item, index) in arr" :key="index">
        <span> {{ item.name }}</span>
        <button @click="addbtn(index)">添加</button>
        <button @click="delbtn(index)">删除</button>
      </li>
    </ul>
    <table border="1" width="500" cellspacing="0">
      <tr>
        <th>序号</th>
        <th>书名</th>
        <th>单价</th>
        <th>数量</th>
        <th>合计</th>
      </tr>
      <tr v-for="(obj,ind) in arr" :key="ind">
        <td>{{ind + 1}}</td>
        <td>{{obj.name}}</td>
        <td>{{obj.price}}</td>
        <td>{{obj.count}}</td>
        <td>{{obj.price * obj.count}}</td>
      </tr>
    </table>
    <p>总价格为:{{total}}</p>
  </div>
</template>

<script>

export default {
  data() {
    return {
      arr: [
        {
          name: "水浒传",
          price: 107,
          count: 0,
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
        },
      ],
    };
  },
  methods: {
    addbtn(m){
      this.arr[m]['count']++
    },
    delbtn(n){
      if(this.arr[n].count === 0){
        return alert('请添加购物车！')
      }
      this.arr[n]['count']--
    }
  },
  computed:{
   total(){
    return this.arr.reduce((item,index) => {
      return item += index['price'] * index['count']
    },0)
   }
  }
};
</script>